package cn.hdu.liang.polymorphism;

class Useful {
    public void f() {

    }

    public void g() {

    }
}

class MoreUseful extends Useful {
    public void f() {

    }

    public void g() {

    }

    public void u() {

    }

    public void v() {

    }

    public void w() {

    }
}

public class RTTI {
    public static void main(String[] args) {
        Useful[] x = {new Useful(), new MoreUseful()};
        x[0].f();
        x[1].g();
        ((MoreUseful) x[1]).u();
        String s = x[0].getClass().getSimpleName();
        System.out.println(s);
        if("MoreUseful".equals(s)) {
            ((MoreUseful) x[0]).u();
        }
    }
}
